Adorable photos: Bison calves born at zoo in Illinois

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Two five-year-old females each gave birth to one calf in recent weeks. Leotie had a male calf born May 31, 2014, and Lucy had a female calf born June 6. A 14-year-old bull, named Ron, is the sire of both calves according to zoo officials.

Calves typically weigh 40 to 50 pounds at birth according to the zoo’s website. They are born with a reddish coat, and it takes about 15 weeks for their coat to change to dark brown in color. The calves can stand within about a half-hour of birth, and they can run after just a few hours. They nurse for several months but also begin grazing within a week of being born.

“Some refer to bison as buffalo, which is theoretically inaccurate. True buffalo are native only to Asia and Africa. A member of the bovine family, bison are the largest land animal in North America,” according to the Brookfield Zoo website.